Along with miniaturization of an optical module, it is required to lower height of the optical fiber used in the vicinity of the optical module (to suppress low the height of the optical fiber from an electronic substrate or the like to which one end of the optical fiber is vertically connected).
In order to lower the height of the optical fiber, it is common to use a bent optical fiber obtained by formation of a bent portion at one end of the optical fiber. However, an amount of distortion to an outer periphery becomes excessively large when, for example, a part of the optical fiber is simply bent into a radius of curvature R (a curvature d [1/mm] is a reciprocal of the radius of curvature R) of 3 [mm] or less in order to form the bent portion. In such a situation, a possibility that the bent optical fiber is broken by excessive distortion increases. Therefore, a method of removing the distortion of the bent portion by heating the bent portion is often adopted. The following Patent Document 1 discloses a technology in which an optical fiber is melt by heating means using discharge and bending processing is performed. Note that, in the present specification, the bending processing in which the optical fiber is heated in this way is hereinafter referred to as heating bending processing. In contrast, the bending processing in which the optical fiber is not heated is hereinafter referred to as non-heating bending processing.